Chair back support



FIG. 1 is a front perspective view of a chair back support, in accordance with the present invention;

FIG. 2 is a front elevation view of the chair back support shown in FIG. 1;

FIG. 3 is a back elevation view of the chair back support shown in FIG. 1;

FIG. 4 is a left side elevation view of the chair back support shown in FIG. 1;

FIG. 5 is a right side elevation view of the chair back support shown in FIG. 1; and,

FIG. 6 is a top plan view of the chair back support shown in FIG. 1.

The broken lines shown in the drawings are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a chair back support, as shown and described. 